I do know that running boards have a taller "skirt" on the big trucks than the small trucks, thus the cab down to running board measurement is different for big and small trucks.
This could be a factor depending on how much of the patch panel you need to use, as the fender lines up with both cab and running board.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-